A long time ago I bought a flexible solar panel (the type you stick on boats or strap to the boom). Just to play with. It is a Uni-Solar 5W(!) panel.
I soon found that you have to have something to stop the panel drawing current when the sun doesn't shine. Back in the box for a bit (where a bit is of undefined length).
I'm now thinking of playing with it again and am looking for a simple controller.
There are loads of apparently different brands on Amazon for around £10 upwards.
formatting link
A remarkable number seem to have the LCD screen, USB ports, buttons etc. all in identical places which suggests that they may all be one product (or at least underlying board).
formatting link
seems to show this more markedly.
Does anyone have any experience of these, perhaps enough to make a recommendation?
Daughter had an electric fence around a rabbit hutch, powered by a 12V
17Ah sealed battery. On every night and if the area wasn't attended (= my Mum was away <g>) and the battery would last (safely) over a week.
I added a 5W solar panel and one of the LCD / USB controllers you mentioned and the battery would then last nearer 3 weeks.
The reason it wasn't more was mainly down to the fact the panel wasn't anywhere near optimally mounted, in fact it would only be exposed to any real sunlight for a couple of hours each day.
The real reason for adding the controller was it allowed the electric fence to run automatically only dusk to dawn and protected the battery from over discharge.
The 'problem' with any of these controllers and smaller panels is the parasitic energy they draw to run themselves.
I could have re-orientated the panel, got a bigger panel or put another panel at the other end of the building (to catch the sun later in the day) but it was easier to just swap the battery for it's partner and on an Optimate 2 charge / maintainer.
So, unless you know the overall balance of the system (worst case energy in V typical energy out) is 'suitable' for your needs and so if a controller is 'worth it', you may be better off with just an anti-discharge protection diode.
Whilst a controller is a must to protect a battery from overcharge, if the panel can deliver more current (and voltage) than the battery should get once fully charged, the use of one with smaller panels (where the ability of the panel is offset by the self discharge of the controller) only really works to protect the battery from over discharge, ironically, partially caused by the controller itself.
Stikes me as a good way to use all the 5W (in bright direct sunlight) output of the panel, giving no nett benefit...
Wouldn't be surprised, lots of gadgets are based on the same underlying chipset if not board.
The "controller" in my small solar panel is nothing more than a series schotty diode and a self flashing blue LED. When the LED is on the battery doesn't get charged unless the panel is well illuminated. Schotty diode as they have less forward volt drop than silicon.
On Sat, 27 Jun 2020 07:22:11 -0700 (PDT), snipped-for-privacy@gmail.com wrote: <true>
True, but it doesn't prevent any overdischarge of the battery?
The trick is to find a LVD solution that doesn't draw any significant current itself, or find one where the LVD draws far less than any potential load.
A latching relay / circuit might be such and could be used to disconnect itself and the load when the LV threshold was detected.
I don't recall the op requesting a discharge protecting relay. If he wants one, I would not regard it as a trick in any way, just some basic electronics. A bistable relay can eliminate most of the current draw. Drive it with a low current opamp, 2 transistors or fets & 2 big caps and Robert's your relative.
He didn't specifically request a lot of things but did request general advice.
'Basic electronics' that provides the LVD function whilst not consuming any power itself?
I know, I suggested it.
Schematic? ;-)
The point was, whilst a simple series diode can negate any self discharge by the panel (and should be built into most panels in any case), a big hole many fall into is wrecking a perfectly good / expensive battery by over discharging it. So, it might be considered 'better' to have a less efficient system that protects the battery than a more efficient one without.
The OP was looking for feedback from people who had experience of the items he referenced, and I have ... and one of the 'virtues' is that they typically protect the battery from over discharge.
I wonder if it oscillates around the cut off point. 0.3V hysteresis seems too low. Battery under load gets to 12.4V and the circuit cuts off the output. Battery no longer under load and recovers to 12.7V and circuit restores output. Battery now under load at 12.4V and ..........
Any circuit that requires a heat sink in such a small enclosed die cast box is going to run at elevated temperatures. I personally would have chosen a capacitor temperature rated at 105C
That would depend on the channel resistance and the load current. As to what extent it would heat up.
I thought the voltage trip values a bit silly, but using the datasheet, you can likely adjust it.
A tight hysteresis loop like that, might be intended for cases where the solar panel cannot provide an infinite amount of power, the "application" requires motor power at fairly closely spaced intervals, and so the time to charge is being reduced a bit. So the thing runs in "spurts".
If you set the hysteresis for the entire battery charging range, it might take a number of hours for the battery to refill, and maybe the barrel full of water overflows or something.
I suppose there's a value statement involved here, about what the output resistance of a battery is. If the battery is elderly, you might well run into cases where that circuit oscillates. If the battery is "solid", then it'll be unflappable at low load.
My car battery went from 12.8V to 9V with a 150A load on it. But I couldn't tell you whether that's a "healthy" battery or not.
4V for 150A. At 25A, that would be 4/6V or 0.66V, which would run afoul of the tight hysteresis. So maybe a 10A load would be OK. Even if the circuit had a fuse, we'd have some idea what he had in mind :-) But there's no fuse. Short the output and see what that MOSFET can take ???
The chances are there is something like that built into the charge controllers you referenced (there certainly was in the one with two USB outlets as that's the one we used for a couple of years).
I went to turn the electric fence off and found it was already off. Then I checked to battery voltage (LCD display) and realised why (it had gone into LVD mode and it hadn't been sunny enough, long enough to re-trigger it again).
When I was looking for a suitable charge controller (again, really for the LDV function) I was looking for something 'lightweight' that might have a correspondingly low parasitic load but couldn't find anything.
The thing is, if the charge to total load capability it's sufficient to stop the battery flattening in the first place, not having it auto reset may still be 'better' than destroying a battery?
I have re-cycled too many 'brand new, used a couple of times' batteries from motorcycles and other roles from lack of maintenance to know I'd rather avoid that over anything else.
If you manage to invent electronics tht uses no power I'm sure the world will be curious. Do you have any other silly requests?
feel free.
There are sound reasons why they aren't. If you run panels in series you don't benefit from multiple V drops. There are also ways to prevent discharge that don't drop a volt or so under load.
Yes. And some are more careful. And in some situations it's better to run it low on infrequent occasion than cut off early etc.
It's hard to know what the op wants without enough detail.
Well, if that's what you want to do I'm not sure the fact that 'the switch happens to waste energy (because it's not 100% efficient) is the issue is it? The issue here was nor wasting *unnecessary* energy that *isn't* part of the desired load (even if the load itself is inefficient etc)?
Then in the absence of a better alternative, that's part of the deal.
Quite?
So, the issue is back to ... can you afford to keep replacing over-discharged (with best case reduced recycle count, worst case completely ruined (sulphated, if LA) batteries or are you willing to sacrifice some capacity for their protection? Yes / No.
The alternative would be to do things like:
Cycle the battery manually with a mains charged one every 'n' interval (where n was fairly constant pre the addition of the controller / solar panel) V n + x, where x is the time gained as a function of adding the solar panel?
Monitor the battery voltage manually and remove it before it went below a safe threshold.
Monitor the battery remotely and remove it (or the load, add the charger etc) before it became over-discharged.
Ensure the worst case load V charge never goes negative.
Ensure the capacity of the battery is large enough to maintain the load between instances of sufficient charge (if the load isn't constant etc).
I wasn't trying to, I was suggesting such didn't exist.
Do you have any other stupid statements (before you dig the hole deeper and then hiding etc).
No, you were the one suggesting it was fixable with some 'basic electronics'? You tell me what they are (before you confirmed such didn't exist etc).
I know. I was talking of the sort of panel sold to maintain a 12V battery.
Agreed.
There are?
Of course? Duh!
Of course ... other than for the lifespan of the battery (with LA specifically). I'm not sure the OP is thinking on running some life support kit off this solar panel. ;-)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.